Plasticos

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  • Publicado : 23 de noviembre de 2010
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PE Polyethylene

Polyethylene is a semi-crystalline thermoplastic with high toughness and chemical resistance, low mechanical strength in comparison to other plastics and cannot be used at high temperatures. The individual polyethylenes differ in regard to their molar mass (molecular weight), which is important for the respective physical properties. This means that in addition to the commonproperties that all types have, certain ones have type-specific properties. The polyethylene semi-finished products that we offer - from which we also manufacture finished products - consist of high density polyethylene types produced by extrusion or moulding processes.
Main properties:
• low density compared to other materials (0.94 g/cm3)
• high impact resistance, also at lowtemperatures
• Minimum water absorption (< 0.01%)
• excellent chemical resistance
• high corrosion resistance
• Anti-adhesive
• very good electrical insulator
• high vibration absorption
• physiologically safe (does not apply to reprocessed semi-finished products)
Sliding properties
PE-HD (PE 300; molar mass approx. 200,000 g/mol) is very suitable for welding due to itsrelatively low molar mass; however, it is not abrasion resistant and has low stability values. This leads to a high level of sliding abrasion, which excludes its use in sliding applications. PE-HMW (PE 500; molar mass approx. 500,000 g/mol) has better sliding properties because of its higher molar mass and is also more abrasion resistant than PE-HD. In combination with its good toughness, it issuitable for use in low stress components that are not subject to any high degree of sliding abrasion. PE-UHMW (PE 1000; molar mass approx. 4,500,000 g/mol). Because of its high molar mass it has very good wear resistance, bending strength and impact resistance and good noise absorption. Due to its excellent sliding properties and low sliding abrasion, it is the ideal material for lightly loadedcomponents. Both PE-HMW and PE-UHMW are also available as reprocessed materials, although it must be noted that the respective physical properties are slightly reduced.
Chemical resistance
All PE types are resistant to acids, alkaline solutions, salts and salt solutions, alcohols, oils, fats, waxes and many solvents. Aromatics and halogenated hydrocarbons cause swelling. All PE types are notresistant to strong oxidising materials (e.g. nitric acid, chromic acid or halogens), and there is a danger of stress corrosion cracking.
Machining
In addition to the good welding properties of PE-HD and PE-HMW, all PE types can also be machined. The semi-finished products can be drilled, milled, awed, planed and turned on a lathe. It is also possible to cut a thread into the material or insert athreaded element. As a rule, no cooling or lubricating emulsion is necessary.

PP Polypropylene

Polypropylene is a semi-crystalline thermoplastic with high rigidity and very good chemical resistance. Characteristic for polypropylene is a CH3 side-group in the monomer structural unit, which can be aligned in various spatial positions during polymerisation.
Main properties:
• low densitycompared to other materials (0,91 g/cm3)
• Minimum water absorption (< 0.01%)
• excellent chemical resistance, also to solvents
• high corrosion resistance
• relatively high surface hardness
• very good electrical insulator
• physiologically safe
Sliding properties
PP-H is subject to strong sliding abrasion and is thus not suitable for use in sliding applications.
Chemicalresistance
PP-H is resistant to acids, alkaline solutions, salts and salt solutions, alcohols, oils, fats, waxes and many solvents. Aromatics and halogenated hydrocarbons cause swelling. PP-H is not resistant to strong oxidising materials (e.g. nitric acid, chromic acid or halogens) and there is a danger of stress corrosion cracking.
Machining
In addition to its good welding properties, PP-H...
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